Enhanced Autoionization of Water at Phospholipid Interfaces

*S Supporting Information ABSTRACT: The structure and autoionization of water at the water−phospholipid interface are investigated by ab initio molecular dynamics and ab initio Monte Carlo simulations using local density approximation (LDA) and generalized gradient approximation (GGA) for the exchange−correlation energy functional. Depending on the lipid headgroup, strongly enhanced ionization is observed, leading to the dissociation of several water molecules into H+ and OH − per lipid. The results can shed light on the phenomena of the high proton conductivity along membranes that has been reported experimentally. Phospholipids are amphiphilic molecules that, in an aqueous environment, self-assemble into bilayers and form the major structural constituents of biomembranes. Although the affinity of the lipid’s headgroup to interfacial water has been widel